ABSTRACT
The main objectives of research in chemistry in the last century or so are the determination of the structure and properties of molecular species, the characterization of its reactive propensity, and the elucidation of the mechanisms of the reactions in which they are involved. In the last few decades, chemistry has greatly evolved toward a less empirical science in which molecular structures, chemical reactivity, and reaction mechanisms are explained from the characterization of the electronic density. In this context, the conceptual density functional theory (CDFT) and the quantum theory of atoms in molecules (QTAIM) have been crucial for such a development.1,2 On one hand, pioneer works by Parr, Geerlings, Chattaraj, and many others have set the foundation of CDFT, providing theoretical support for empirical concepts that chemists have used for years on an intuitive basis. Rigorous definitions of properties such as electronegativity,3-5 hardness,6 and electrophilicity,7,8 together with easy ways to compute them and the formulation of reactivity principles and postulates that gives them an interpretative basis, have produced speedy development of the field of computational chemical reactivity. On the other hand, the works by Bader and collaborators on the characterization of the Laplacian of the electron density
12.1 Introduction .................................................................................................. 253 12.2 Four Concepts ............................................................................................... 255
12.2.1 Reaction Force .................................................................................. 255 12.2.2 Partition of Activation Energy ..........................................................256 12.2.3 Reaction Force Constant ................................................................... 258 12.2.4 Reaction Electronic Flux (REF) ....................................................... 259
12.2.4.1 Characterization of Electronic Activity Using REF .......... 261 12.3 Concluding Remarks ....................................................................................265 Acknowledgments ..................................................................................................265 References ..............................................................................................................266
